pregnancy and childbirth

gestation

pregnancy, lasts average 266 days

gestational calendar measured from first day of woman’s last menstrual period (LMP)

birth predicted 280 days (40 weeks) from LMP

term

the duration of pregnancy

trimesters

three 3-month intervals in the term

conceptus

all products of conception: embryo/fetus, placenta and associated membranes

blastocyst

the developing individual is a hollow ball for the first 2 weeks

before day 16, a hollow cell cluster

embryo

from day 16-week 8

fetus

from beginning of week 9-birth

attached by umbilical cord to placenta

neonate

newborn-6 weeks old

hormones of the strongest influence on pregnancy

estrogens, progesterone, human chorionic gonadotropin and human chorionic somatotropin

all secreted by the placenta

corpus luteum in first several weeks

the most important source of hormones, if the luteum is removed before week 7 the pregnancy terminates

from week 7-17 the luteum degenerates as the placenta takes over endocrine function

human chorionic gonadotropin (HCG)

secreted by a blastocyst and placenta, it is detectable in urine 8-9 days after conception by at home tests

stimulates the growth of the corpus luteum: secreting a lot of progesterone and estrogen

estrogens

increases to 30 times normal by the end of gestation

corpus luteum is source for first 12 weeks until placenta takes over

causes tissue growth in fetus and mother: enlarging uterus and external genitalia, mammary ducts, and relaxing the pubic symphysis, widening the pelvis

progesterone

secreted by placenta and corpus luteum, suppressing FSH and LH to prevent follicular development during pregnancy

suppressing uterine contractions, preventing premature childbirth and menstruation

promotes proliferation if decidual cells of the endometrium where the blastocyst feeds from

stimulates the development of acini in breast

human chorionic somatomammotropin (HCS)

placenta begins secretion of this at about 5 weeks, the amount that is secreted is steady until term

there is a high concentration of the hormone but the function is poorly understood

effects are similar to growth hormones, but weaker

reduces mothers insulin sensitivity and glucose usage leaving more for the fetus, can lead to gestational diabetes

pituitary gland growth

grows about 50% larger during pregnancy

produces markedly elevated levels of thyrotropin, prolactin and ACTH

thyroid gland greoth

becomes about 50% larger under the influence of HCG, pituitary thyrotrpoin, and human chorionic thyrotropin from the placenta

increasing the metabolic rate of mother and fetus

parathyroid growth

these glands enlarge and increase osteoclast activity

ACTH stimulates…

glucocorticoid secretion

mobilizing amino acids for fetal protein synthesis

Aldosterone secretion rises to promote…

fluid retention and increasing the mothers blood volume

relaxin secreted by the…

corpus luteum and placenta

uses progesterone as well to stimulate multiplication of decidual cells

promoting growth of blood vessels int he pregnant uterus, loosens connective tissues

uterus weight

900g at the end of pregnancy, 50 g when not pregnant

reaches almost to the xiphoid process

babies are born…

headfirst, the head acts as a wedge to widen the cervix, vagina and vulva

the baby turns down around 7 months

fetus role in birth

passive player, the expulsion is achieved by the contractions of mothers uterine and abdominal muscles

the fetus can play a role in the chemical stimulation of contractions signaling that it is developed enough to be born

braxton hicks contractions

relatively weak contractions of the uterus over the course of gestation

false labor, strongest in late pregnancy

parturition

the process of giving birth, marked by the onset of true labor contractions

uterine contractility hormones

progesterone and estradiol balance may be one factor in the pattern of increasing contractility

progesterone inhibits contraction, but its secretion declines after 6 months

estradiol stimulates contractions and rises

contractility at full term

posterior pituitary releases more oxytocin (OT), uterus produces more OT receptors

oxytocin produces labor in 2 ways

stimulates muscles of myometrium

stimulates fetal membranes to produce prostaglandins, which are synergists to OT in producing labor contractions

fetal cortisol

the levels of this rise and may increase estrogen secretion by the placenta

released by the placenta and fetus

fetal pituitary releases OT to stimulate…

fetal membranes to produce prostaglandin

uterine stretching

plays role in initiating labor, the stretching of smooth muscle increases contractility

labor contractions

they bagin about 30 mins apart and eventually make it to 1-3 mins apart

periodically relax to increase blood flow and oxygen delivery to the placenta and fetus

they are the strongest in the fundus and body of the uterus, weakest in cervix to push the fetus down

positive feedback theory of labor

labor is induced by the stretching of the cervix, triggering reflex to contract uterine body, pushing uterus down and stretching the cervix even more

self amplifying cycle of stretch and contraction

neuroendocrine reflex

induced by cervical stretching, it goes through the spinal cord, hypothalamus and posterior pituitary

posterior pituitary releases oxytocin: carried through blood to stimulate uterine muscles

positive feedback steps

Cervical stretching → oxytocin secretion → uterine contraction → cervical stretching

induced labor drug

pitocin, it mimics oxytocin

valsalva maneauver

contracting abdominal muscles to increase pressure of the abdominal area to expel the fetus

ischemia of the myometrium

the first pain of labor. the muscles hurt when theyre deprived of blood and contractions resist circulation

pain when fetus enters vaginal canal

the pain becomes stronger because the cervix, vagina and perineum stretch. may even tear

episiotomy

an incision in the vulva to widen the vaginal orifice to prevent random tearing

pain is a product of 2 factors

unusually large brain and head of the infant

the narrow pelvic outlet that allows for bipedal walking

c section consequences to the mother

higher risk of infection, organ damage

higher risk to subsequent pregnancies

c section baby consequences

changes to the gut microbiome

respiratory distress, immune system consequences

higher rate of noncommunicable disease: allergies, type 1 diabetes and celiac

three stages of birth

dilation, expulsion and placental stage

stage duration tends to be longer in primipara (first birth), shorter in multipara (previously given birth), and shortest in grandmultipara (given birth 5 times)

dilation stage

longest stage, 8-24 hours, dilation to 10cm of cervical canal and effacement (thinning) of cervix

rupture of fetal membranes and loss of amniotic fluid: water breaking

late dilation: dilation reaches 10 cm in 24 hrs or less in primipara and in as little as a few mins in multipara

expulsion stage

from entry of head into vagina until baby is expelled, 30-60 mins in primi; shorter in multipara

after expulsion, attendant drains blood from umbilical vein into baby. clamping the umbilical cord and cutting it

crowning

when a baby’s head is visible, expulsion stage

delivery of head is most difficult part

placental stage

uterine contractions cause placental separation

membranes (afterbirth) inspected to be sure everything has been expelled

first 6 weeks postpartum

puerperium, period where mothers anatomy and physiology stabilize and reproductive organs return nearly to pre-gravid stage

pre-gravid stage

condition prior to pregnancy

involution

shrinkage of the uterus, loses 50% of its weight the first week

achieved by autolysis (self-digestion) of uterine cells by their own lysosomal enzymes

for about 10 days, it produces lochia

lochia

the vaginal discharge that comes for about 10 days postpartum, starts off bloody then turns serous

breastfeeding

promotes involution, suppresses estrogen secretion which would make the uterus more flaccid

stimulated oxytocin to cause myometrium to contract and firm up the uterus sooner

lactation

the synthesis and ejection of milk from the mammary glands

last as little as 1 week in women who dont breastfeed

can continue for many years as long as the breast is stimulated by nursing or pumping

traditionally nurse for about 2.8 years

high estrogen in pregnancy causes…

ducts of mammary glands to grow and branch

all hormones that help develop mammary glands

growth hormone, insulin, glucocorticoids and prolactin

progesterone stimulates the…

budding and development of acini at the end of the ducts

acini are organized into clusters called…

lobules within each breast lobe

colostrum

forms in late pregnancy, similar to breast milk in protein and lactose but contains one third more fat

sole nutrition source for first 1-3 days after birth

thick consistency and a cloudy yellow color

contains IgA to protect baby from gastroenteritis

prolactin, from anterior pituitary

promotes milk synthesis, inhibited by dopamine when not pregnant

synthesis of hormoes begins at 5 weeks into pregnancy, by term its 10-20 times normal level

has a little effect on mammary glands untiul after birth since steroids from placenta oppose it

milk synthesis requires 4 hormones to mobilize necessary amino acids, fatty acids, glucose and calcium

growth hormone, cortisol, insulin and parathyroid hormone

prolactin levels after birth

at birth, the secretion of this drops to non-pregnancy levels

every time the infant nurses it jumps 10-20 times its level for an hour

stimulating synthesis of mink for next feeding and without nursing the production stops in 1 week

low pregnancy rate during breastfeeding

only 5-10% of women become pregnant while breastfeeding, the inhibition of GnRH and reduced ovarian cycling is the reason

this allows for natural spacing of births

milk ejection

the milk is continually secreted into mammary acini, but it doesn’t easily flow into the ducts

the ejection (letdown) is controlled by a neuroendocrine reflex

infant suckling

this action stimulates sensory receptors in nipple, signaling hypothalamus and posterior pituitary to release oxytocin

oxytocin stimulates myoepithelial cells around each acinus

contracts to squeeze milk into duct: flow within 30-60 seconds after suckling begins

breast milk changing composition

changes over the first 2 weeks, varies from one day to another

varies over 20 minute feeding: at the end of a feeding there is less lactose and protein, but six times the fat

cows milk isn’t a good breastmilk substitute

there is one third less lactose but three times as much protein

its harder to digest and more nitrogenous waste (diaper rash)

meconium

green, bile filled fecal material in newborn

the colostrum and milk have a laxative effect that clears the intestine

breastmilk

supplies antibodies and colonizes intestine with beneficial bacteria

nursing women can produce 1.5 L of milk per day

contraception

any procedure or device intended to prevent pregnancy

behavioral contraception

abstinence, rhythm method (periodic abstinence) and withdrawal (coitus interruptus)

barrier and spermicidal contraception methods

male and female condom, diaphragm or sponge

spermicides: foams, creams, jellies

hormonal contraception methods

preventing ovulation

the pill, morning after pills, RU-486

the pill

estrogen and progestin, patch, injection, or vaginal ring

ovarian follicles do not mature as FSH, LH are inhibited

morning after pills

emergency contraceptive pills, high dose of estrogen and progestin or progestin alone

induce menstruation if implantation hasn’t occurred

inhibits ovulation, inhibits sperm movement, inhibits implantation

intrauterine device (IUD)

springy device that is left in place for extended period of time

irritates uterine lining and interferes with implantation

surgical sterilization

clamping or cutting the genital ducts (uterine tube or ductus deferens)

tubal litigation in females, vasectomy in males